KR20190097173A - Polytetrafluoroethylene porous membrane, waterproof breathable membrane and waterproof breathable member using the same - Google Patents

Abstract

The polytetrafluoroethylene (PTFE) porous membrane of the present disclosure is a membrane having an average fibril length of 50 µm or more, an average node length of 5 times or more of an average fibril length, and an average node area ratio of 5% or less. When the PTFE porous membrane of the present disclosure is installed in a housing such as an electric component and an electric product as a waterproof ventilation membrane, water vapor remaining in the housing can be discharged to the outside of the housing more quickly.

Description

Polytetrafluoroethylene porous membrane, waterproof breathable membrane and waterproof breathable member using the same

The present invention relates to a polytetrafluoroethylene (hereinafter referred to as PTFE) porous membrane, a waterproof ventilation membrane and a waterproof ventilation member using the same.

In some cases, waterproof ventilation membranes may be provided in the housings of vehicle electrical components such as lamps, pressure sensors, ECUs (Electronic Control Units), secondary battery storage cases, and various electrical appliances. By installing the waterproof ventilation membrane, a ventilation path between the outside and the inside of the housing is secured, so that pressure fluctuations inside the housing accompanying temperature change can be alleviated, or gas generated inside the housing can be discharged to the outside. In addition, the waterproof ventilation membrane can suppress intrusion of foreign matter such as water and / or dust from the outside of the housing through the ventilation path.

Waterproof breathable membranes having a PTFE porous membrane are known. Patent Document 1 discloses a PTFE porous membrane that can be used for a waterproof ventilation membrane.

Resin having relatively high hygroscopicity, such as polyamide (PA), polycarbonate (PC), and polybutylene terephthalate (PBT), may be used for the housing of electrical components and electrical appliances. The housing in which such a resin is used absorbs the surrounding water vapor, but the absorbed water vapor is released by heat from a heat source inside the housing or heat from the outside such as sunlight, and a part thereof stays inside the housing. It is desired that water vapor inside the staying housing be discharged to the outside of the housing as soon as possible.

The waterproof ventilation membrane serves as a barrier to the rapid release of water vapor. For this reason, it is proposed to promote the discharge of water vapor by forced convection. For example, Patent Document 2 discloses a system in which a piezoelectric blower is installed in a housing to quickly discharge water vapor from the housing. It is also proposed to use natural convection. For example, the headlamp of a vehicle disclosed in Patent Document 3 includes a first ventilating body provided in front of the light source of the lamp and a second ventilating body provided behind the light source, and the ventilation amount of the first ventilating body. It is set larger than the ventilation amount of this 2nd ventilation body. In this system, natural convection by heat radiated forward from the light source is used.

Japanese Patent Laid-Open No. 50-22881 Japanese Patent Publication No. 2013-229281 Japanese Patent Laid-Open No. 2015-109206

It is an object of the present invention to provide a new technique suitable for quickly discharging water vapor retained inside a housing to the outside of the housing.

The present invention provides a PTFE porous membrane having an average fibril length of 50 µm or more, an average node length of 5 times or more of an average fibril length, and an average node area ratio of 5% or less.

In another aspect, the present invention provides a waterproof breathable membrane comprising the PTFE porous membrane of the present invention.

In still another aspect, the present invention provides a waterproof ventilation member including the waterproof ventilation membrane of the present invention and a support bonded to the waterproof ventilation membrane.

Attempts have been made to realize the promotion of the discharge of water vapor from the housing by the improvement of the PTFE porous membrane itself. The PTFE porous membrane according to the present invention can have a high moisture permeability in the film thickness direction that has not been conventionally present. High moisture permeability means that the permeation rate of water vapor due to diffusion in the porous membrane is large. Thereby, in the PTFE porous membrane according to the present invention, when installed in the housing as a waterproof ventilation membrane, water vapor remaining in the housing can be discharged to the outside of the housing more quickly. In addition, the moisture permeability and breathability of the membrane are different concepts. The discharge of "stayed" water vapor inside the housing includes the discharge of water vapor in the absence or weakness of the inside and outside of the housing. The discharge of the water vapor retained inside the housing, which includes the discharge in this state, is not facilitated by the increase in the ventilation of the membrane.

The PTFE porous membrane according to the present invention is suitable for quickly discharging water vapor from inside a housing without using a ventilation means such as a piezoelectric blower requiring energy input. In addition, the discharge of water vapor using the PTFE porous membrane according to the present invention is highly versatile and can be applied to a wide product without being limited to a headlamp.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram for demonstrating the influence of the average node area ratio of the said membrane on the moisture permeability of the membrane porous direction of a PTFE porous membrane.
It is a schematic diagram for demonstrating the influence of the average fibril length of the said membrane on the moisture permeability of the membrane porous direction of a PTFE porous membrane.
It is a schematic diagram for demonstrating the influence of the average node length of the said membrane on the moisture permeability of the membrane porous direction of a PTFE porous membrane.
4 is a schematic view for explaining an example of a membrane structure that the PTFE porous membrane of the present invention can have.
It is sectional drawing which shows typically an example of the waterproof ventilation film of this invention.
It is a perspective view which shows typically an example of the waterproof ventilation member of this invention.
It is a top view which shows typically an example of the waterproof ventilation member of this invention.
FIG. 8: is a figure which shows the observation image by the scanning electron microscope (henceforth SEM) of the PTFE porous membrane produced in Example 1. FIG.
It is a figure which shows the observation image by SEM of the PTFE porous membrane produced in Example 2. FIG.
FIG. 10: is a figure which shows the observation image by SEM of the PTFE porous membrane produced by the comparative example 1. FIG.
It is a figure which shows the observation image by SEM of the PTFE porous membrane produced by the comparative example 2. FIG.

The PTFE porous membrane according to the first aspect of the present disclosure is a membrane having an average fibril length of 50 µm or more, an average node length of 5 times or more of an average fibril length, and an average node area ratio of 5% or less.

In the second aspect of the present disclosure, for example, the PTFE porous membrane according to the first aspect is a membrane whose average node area ratio is 3% or less.

In the 3rd aspect of this indication, the PTFE porous membrane which concerns on a 1st or 2nd aspect, for example is a membrane whose average curvature ratio in a film thickness direction is 1.5 or less.

In the fourth aspect of the present disclosure, for example, the PTFE porous membrane according to any one of the first to third embodiments has a water pressure measured based on the water resistance test B method (high water pressure method) of JIS L1092. It is more than 10. However, the water pressure resistance is evaluated based on the water pressure when water emerges from one place of the membrane surface of the PTFE porous membrane.

In the fifth aspect of the present disclosure, for example, the PTFE porous membrane according to any one of the first to fourth aspects is a membrane having a porosity of 90% or more.

In the sixth aspect of the present disclosure, for example, the PTFE porous membrane according to any one of the first to fifth aspects has a water vapor transmission rate of 150000 g measured in accordance with the provisions of JIS L1099 (B-1 method). / (M 2 · day) or more.

The waterproof air permeable membrane which concerns on the 7th aspect of this indication is equipped with the PTFE porous membrane which concerns on any one of 1st-6th.

The waterproof ventilation member according to the eighth aspect of the present disclosure includes the waterproof ventilation membrane according to the seventh aspect and a support bonded to the waterproof ventilation membrane.

For the PTFE porous membrane of the present invention, the water vapor transmission rate in the film thickness direction measured in accordance with the provisions of JIS L1099 (B-1 method) may be 150000 g / (m 2 · day) or more. Depending on the structure of the porous membrane, the water vapor permeability is more than 150000 g / (m 2 · day), 155000 g / (m 2 · day) or more, 160000 g / (m 2 · day) or more, 180000 g / (m 2 · day) or more, further 200000g / M 2 · day) or more. The upper limit of the said water vapor transmission rate is not limited, For example, it is 300000 g / (m <2> * day) or less. In the PTFE porous membrane of the present invention, the moisture permeability in the film thickness direction measured based on the provisions of JIS Z0208 (moisture permeability test, cup method) is, for example, 9000 g / (m 2 · day) or more, depending on the configuration of the porous membrane. May be 10000 g / (m 2 · day) or more, further 11000 g / (m 2 · day) or more. The upper limit of the said water vapor transmission rate is not limited, For example, it is 16000 g / (m <2> * day) or less.

Moreover, when the test piece which is a measurement object of water vapor transmission rate is too small to apply the measurement by JIS as it is, a water vapor transmission rate can be measured using an auxiliary plate. For example, in the method specified in JIS L1099 (B-1 method), the opening of the cup holding a moisture absorbent (potassium acetate solution) is brought into contact with a test piece having a size of about 200 x 200 mm fixed by a test piece support frame. It is supposed to be. If the size of the test piece is smaller than the size described above, the test piece is fixed so as to cover the opening provided in the center of the auxiliary plate having an outline conforming to the shape of the inner circumference of the test piece supporting frame (circle of 80 mm in diameter), and the auxiliary plate is What is necessary is just to fix in a support frame. A double-sided adhesive tape can be used to fix the test piece to the auxiliary plate and to fix the auxiliary plate to the support frame. As the auxiliary plate, a plate made of metal such as stainless steel is suitable. According to the actual measurement of the present inventors, even if the opening of the auxiliary plate was smaller than the effective area (about 24.6 cm 2) of the cup, the measured value using the auxiliary plate was in good agreement with the measured value by the method not using the auxiliary plate. In JIS Z0208 (moisture permeability test, cup method), although calcium chloride is used as a moisture absorbing agent, the measuring method using an auxiliary plate is similarly effective.

An auxiliary plate can also be used for the measurement of the test piece smaller than the test piece size (about 150 mm x 150 mm) prescribed | regulated to JIS also about the measurement by the water resistance test B method (high water pressure method) of JISL1092. One example of the auxiliary plate is a plate made of stainless steel having a diameter of 47 mm with a circular opening having a diameter of 6 mm at its center. Also in the measurement of the water pressure, it has been confirmed that the use of the auxiliary plate does not substantially affect the measured value.

The PTFE porous membrane of the present invention is a membrane having an average fibril length of 50 µm or more, an average node length of 5 times or more of the average fibril length, and an average node area ratio of 5% or less. Hereinafter, the PTFE porous membrane of this invention which has the said membrane structure is described as porous membrane A. FIG.

The PTFE porous membrane is generally composed of a node (nodule) that is an agglomerated portion of PTFE and anhydrous fibrils that are fine fibrous structures in which both ends are bonded to the node. Adjacent nodes are connected by fibrils. The PTFE porous membrane has air permeability in the film thickness direction, with a space (pore) between adjacent fibrils serving as a ventilation path. The PTFE porous membrane is also called a stretched porous membrane, and is formed by stretching of a PTFE sheet which is an aggregate of PTFE. Nodes and fibrils are formed by the stretching of the PTFE sheet, and these configurations are changed depending on, for example, the stretching conditions of the PTFE sheet.

The PTFE porous membrane A has a specific range of average fibril length, average node length, and average node area ratio. As a result, the PTFE porous membrane A can have high moisture permeability in the film thickness direction.

When passing through a PTFE porous membrane, the water vapor must diffuse to avoid the nodes and fibrils of the membrane. At this time, if the diffusion path of water vapor in the film thickness direction is a configuration of a node and fibrils that become as straight as possible in the film thickness direction of the porous film, the moisture permeability of the film thickness direction in the porous film is increased. The above-mentioned specific fibrillated length, average node length, and average node area are suitable for realizing the diffusion path of linear water vapor in the PTFE porous membrane.

An average node area ratio is demonstrated. As shown in FIG. 1, when the PTFE porous membrane 1 is viewed in a cross section in the thickness direction, in the cross section, a plurality of nodes 2a, 2b, 2c... Are in-plane directions and thicknesses of the porous membrane 1. It exists in both directions of a direction. In addition, although FIG. 1 and the following FIG. 2, FIG. 3 show the form in which the node 2 extended in the same direction in order to simplify description and make it easy to understand, this has shown this invention to this form. It is not intended to be limiting. The water vapor 3 which is to be diffused and moved in the film thickness direction in the porous membrane 1 must move to avoid the node 2 which is an obstacle of diffusion. For this reason, the water vapor 3 which permeate | transmitted between the nodes 2a and 2b cannot spread | diffuse and move linearly in the film thickness direction of the porous membrane 1 by presence of the node 2c, for example, It is inevitable to take the diffusion path 4 to avoid. In the PTFE porous membrane, the bypass of the steam 3 is repeated until the vapor 3 penetrates the porous membrane 1 in the film thickness direction. The moisture permeability of the porous membrane 1 is higher as the diffusion path 4 of water vapor is closer to a straight line, and lower as it deviates from the straight line. Here, the average node area ratio in the PTFE porous membrane A is 5% or less, and the nodes 2a, 2b, 2c, etc. on the diffusion path 4 with respect to the water vapor passing through the porous membrane in the film thickness direction. The obstacles due to this can be alleviated, and the diffusion path 4 can be approached by a straight line extending in the film thickness direction.

The average node area ratio in the PTFE porous membrane A is preferably 3% or less, and more preferably 2.5% or less. The minimum of an average node area ratio is 1.0%, for example. The PTFE porous membrane A having an average node area ratio of 1.0% or more is suitable for achieving desirable waterproofness when used as a waterproof ventilation membrane.

Next, an average fibril length is demonstrated. As shown in FIGS. 2A and 2B, the fibrils 5 of the PTFE porous membrane 1 (only one is shown for simplicity of explanation and for easy understanding) have both ends thereof. It is connected to the node 2. In other words, the average length of the fibrils 5 (average fibrils length) reflects the distance d between the adjacent nodes 2. In other words, the longer the PTFE porous membrane having a longer average fibril length, the longer the distance between adjacent nodes 2. In the PTFE porous membrane having a long distance between adjacent nodes 2, the obstacles caused by the node 2 on the diffusion path 4 can be alleviated with respect to water vapor passing through the porous membrane in the film thickness direction. The diffusion path 4 can be approached by a straight line extending in the film thickness direction.

The average fibril length in PTFE porous membrane A is 50 micrometers or more, and the distance between adjacent nodes is long. In addition, although the water vapor transmission rate is improved by the increase in the average fibril length, an excessively long average fibril length in a state where the average node area ratio is small may lower the strength and / or waterproofness of the porous membrane. In consideration of this, the upper limit of the average fibril length in the PTFE porous membrane A is preferably 90 µm or less. When the average fibril length is 90 µm or less, even when the PTFE porous membrane A is used as a waterproof ventilation membrane, its waterproofness can be more surely improved.

Next, the average node length is described. Water vapor trying to diffuse and move in the membrane thickness direction in the PTFE porous membrane 1 moves not only the node 2 but also the space (pore) between the fibrils 5 to avoid the fibrils 5. . Here, as shown to Fig.3 (a), (b), the fibrill 5 of a PTFE porous membrane is connected to the node 2 at both ends. In the porous membrane having a large average fibril length as described above, as shown in Fig. 3B, when the ratio of the average node length to the average fibril length is small, it is in the direction in which the node 2 extends. As the proportion of the fibrils 5 extending from the perpendicular direction to the inclined direction increases, such fibrils 5 are applied to each of the nodes 2 which exist in the in-plane direction and the thickness direction of the film. It exists to such an extent that it may be countless, and when the whole porous membrane 1 is seen as a whole, the direction from which the fibril 5 extends becomes more disordered. On the other hand, in the porous membrane having a large average fibril length as described above, as shown in Fig. 3A, when the ratio of the average node length to the average fibril length increases, the direction in which the node 2 extends is shown. The proportion of the fibrils 5 extending in a direction perpendicular to and close to the direction (hereinafter, referred to as an approximately vertical direction) increases, and the porous membrane 1 as a whole is dominant (orderly) in that direction. The fibrils 5 are extended. In the most ideal embodiment, when viewed from a direction perpendicular to the main surface of the porous membrane, two adjacent nodes 2 are supported by posts, fibrils 5 are formed, and the two nodes 2 are connected by the nodes 2. A porous structure, also referred to as a ladder, which connects approximately perpendicular to the extending direction, can be formed. In the porous membrane shown in FIG. 3A where the direction is more ordered than in the porous membrane shown in FIG. 3B where the fibril 5 extends more disorderly, the fibrill 5 In order to avoid, the diffusion path 4 of water vapor diffused in the space between the fibrils 5 is close to a straight line extending in the film thickness direction of the film. 3 (a) and 3 (b) are also illustrations for explaining preferred embodiments of the present invention, and the present invention is not limited to the specific embodiments.

The average node length in the PTFE porous membrane A is 5 times or more, preferably 5.5 times or more of the average fibril length. The upper limit of the ratio of the average node length to the average fibril length is, for example, 15.

In addition, the air permeability of the PTFE porous membrane is not affected by the degree of moisture permeability of the membrane, the average node length (the ratio of the average node length to the average fibril length), and the average node area ratio. This presupposes that the air pressure difference occurs between the main surfaces of both sides of the PTFE porous membrane in terms of air permeability, that is, fluid movement is more dominant than diffusion movement with respect to air movement through the PTFE porous membrane when discussing air permeability. Based on that The breathability of the PTFE porous membrane is more strongly affected by the average pore diameter of the membrane.

In this specification, the average fibril length, average node length, and average node area ratio of a PTFE porous membrane are the values calculated | required as follows.

The enlarged image of the main surface of the PTFE porous membrane which is an evaluation target object is obtained by changing at least five places on the main surface by means such as SEM or the like. The means for obtaining the enlarged image is preferably SEM, but is not limited to this, and may be any means capable of sufficiently confirming the form of the nodes and fibrils of the porous membrane. Next, each magnified image is analyzed for image, and the length of at least 10 nodes and the length of at least 10 fibrils are evaluated in an observation area of 1250 µm x 850 µm, respectively. At this time, the node and fibril evaluating the length include the smallest node and fibrils present in the observation region, and the largest length node and fibrils present in the observation region. Next, the average value of the lengths of all the nodes and fibrils (all at least 50 or more) evaluated were obtained, and let this be an average node length and an average fibrillation length. Furthermore, the image area of the 1250 micrometers x 850 micrometers observation image in an enlarged image is image-analyzed, the area ratio (%) of a node is evaluated by the pixel ratio on the said image, and the average value of the said area ratio obtained between the said at least 5 enlarged images. The average node area ratio of the porous membrane is obtained.

The node in the PTFE porous membrane A may extend predominantly in a predetermined direction. The direction is, for example, the transverse direction (TD) direction of the porous membrane, and the TD direction is typically the width direction when the PTFE porous membrane has a band shape. The node in the PTFE porous membrane A may have a high aspect ratio, the width of which is not changed so much in the direction in which the node extends, which is the ratio of the length to the width. The aspect ratio (length / width) may be, for example, 5 or more and 20 or more. The width of the node is, for example, 0.3 μm or more, and may be 1 μm or more, further 2 μm or more. The upper limit of the width of a node is 20 micrometers, for example. In the PTFE porous membrane A, the ratio of short nodes is small. The ratio of the area occupied by the node whose node length is less than 50 micrometers with respect to the total node area may be 10% or less. The PTFE porous membrane A has a low node area ratio of 5% or less while further having an average node length of 5 times or more of a large average fibril length of 50 µm or more.

The fibrils in the PTFE porous membrane A may dominantly extend in a direction substantially perpendicular to the direction in which the nodes extend. The direction is, for example, the MD (machine direction) direction of the porous membrane, and the MD direction is typically the long side direction when the PTFE porous membrane is a band.

In the PTFE porous membrane A, the average curvature ratio in the film thickness direction may be 1.5 or less. The average curvature ratio is a value expressed by the ratio L / L ₀ of the average length L of the diffusion path 4 of water vapor to this, based on the thickness L ₀ of the porous membrane to be evaluated. As can be understood from the above description, the diffusion path 4 means the shortest path of diffusion of water vapor, which extends in the thickness direction of the PTFE porous membrane while avoiding the node 2 and the fibrils 5. The average length L of the diffusion path 4 is governed by the structure of the PTFE porous membrane, more specifically, the structures of the nodes 2 and fibrils 5. The closer the average curvature ratio is to 1, the closer the diffusion path 4 is to the straight line extending in the film thickness direction of the porous membrane 1, and the higher the moisture permeability of the PTFE porous membrane.

The average curvature ratio in the film thickness direction in the PTFE porous membrane A may be 1.3 or less. It is difficult to achieve such a low average curvature rate by the usual stretching method alone. On the other hand, the PTFE porous membrane which has undergone the sticking treatment described later may have such a low average curve.

In this specification, the average curvature ratio of the membrane thickness direction in a PTFE porous membrane shall be the value calculated | required as follows.

Initially, a three-dimensional image including a cross section in the thickness direction of the PTFE porous membrane as an object to be evaluated is obtained by means such as X-ray CT. The means may be any means capable of sufficiently observing the nodes of the porous membrane and the fibrils in the cross section. Next, the cross section of the thickness direction of the film | membrane expressed on the obtained three-dimensional image is image-processed, and the centerline of the space except a node and fibrils is extracted. Subsequently, at least 100 paths through the extracted centerline and penetrating the porous membrane in the thickness direction thereof are selected by an image process per area of 15 µm in width of the cross section, and the average value of the selected shortest path length is obtained. This is called the average length L of the diffusion path 4 in the PTFE porous membrane which is an evaluation object. The obtained average length L is divided by the thickness L ₀ of the PTFE porous membrane to obtain an average curvature ratio of the porous membrane. In selecting the shortest route, the longest route and the shortest route in the region are included.

The PTFE porous membrane of the present invention may have a porosity of 90% or more, for example. The porosity can be at least 93%. Porosity can be calculated | required as follows.

The thickness of the sample obtained by punching the PTFE porous membrane to be evaluated to a predetermined area (17.35 cm 2) is measured with a dial thickness meter (average thickness of 10 points). In addition, the weight W1 of a sample is measured by electronic balance. Subsequently, the volume of the sample was obtained from its area and the average thickness, multiplied by the specific gravity (2.18 g / cm 3) of the calcined PTFE, and the weight of the PTFE calcined body having the same volume as the sample when the porosity was assumed to be zero%. Find W0. Next, the porosity of the PTFE porous membrane can be determined by the formula: Porosity (%) = W1 / W0 × 100.

The water vapor transmission rate of the PTFE porous membrane of this invention can be improved 20% or more by the sticking process mentioned later depending on the structure of the said porous membrane.

The water pressure of the PTFE porous membrane of the present invention (water resistance measured based on the water resistance test method B (high water pressure method) of JIS L1092) is, for example, 10 kPa or more, depending on the structure of the porous membrane, 20 kPa or more. You can also do Such a PTFE porous membrane is suitable for a waterproof ventilation membrane, more specifically, a waterproof ventilation membrane used for the housing of electrical components, such as a lamp. Above all, the use of the PTFE porous membrane of the present invention is not limited to the waterproof ventilation membrane. In the PTFE porous membrane A, although the average node area ratio is small, it may have waterproofness based on the average fibril length in a specific range and the average node length of a large ratio to the average fibril length.

The thickness of the PTFE porous membrane of this invention is 5-60 micrometers, for example, Preferably it is 20-40 micrometers.

The PTFE porous membrane of the present invention may be subjected to a liquid repellent treatment such as water repellent treatment and oil repellent treatment. The liquid repellent treatment of the PTFE porous membrane can be carried out by coating a liquid repellent substance such as a fluorine-based compound, and a known method can be adopted for the coating.

In one embodiment of the PTFE porous membrane of the present invention, the fibrils have branching portions. As shown in FIG. 4, this branch 6 is located between a pair of nodes 2 to which fibrils 5 having the branch 6 are connected at both ends thereof. The branch part 6 is a branch between fibrils 5 to the last, and is not a branch between the node 2 and the fibrils 5. Such a branching part 6 is formed by performing the sticking process which binds several adjacent fibrils 5 with respect to a PTFE porous membrane, for example. It is possible to have two or more branches 6 between a pair of nodes 2, and typically a section in which fibrils 5, which are located between the branches 6 and 6, are bound. (7), the width of the fibrils 5 can be increased. The width of the fibrils 5 in the binding portion 7 is, for example, 5 to 50 times the width of the unbridled fibrils 5 other than the binding portion 7. For example, it may be 0.5 to 5㎛. In addition, the branch part 6 and the binding part 7 are a fiber structure which the several fibrils 5 once formed by extending | stretching a PTFE sheet couple | bonded.

Also in this embodiment, the average fibril length, average node length, and average node area ratio may be in the ranges described above in the description of the PTFE porous membrane A. In addition, the plurality of adjacent fibrils are bundled, so that the spaces 8 between the adjacent binding portions 7 are expanded. For this reason, in this aspect, the moisture permeability of the film thickness direction can be improved further.

Also in this aspect, the fibrils 5 may be fibrils that dominate in a predetermined direction, for example, a direction substantially perpendicular to the direction in which the nodes extend.

The PTFE porous membrane A has a water vapor transmission rate of 150000 g / (m &lt; 2 &gt; Day) It is a new film only in that it is abnormal. In addition, PTFE porous membrane A is a novel membrane only in the point that the water vapor transmission rate of the film thickness direction measured based on the specification of JISZ0208 (Cup method) is 9000 g / (m <2> * day) or more.

The waterproof ventilation membrane of the present invention includes the PTFE porous membrane of the present invention described above. The specific use and use method as a waterproof ventilation membrane are not limited. The waterproof ventilation membrane of the present invention is installed in a housing of a vehicle electrical component such as a lamp, a pressure sensor, an ECU, a secondary battery storage case, or various electrical products, and more specifically, to cover the opening in the opening of the housing. It can be installed and used. By using such a waterproof ventilation membrane, the air permeability between the inside and the exterior of a housing can be ensured, for example, suppressing dust penetration and / or invasion of foreign substances, such as water. In addition, the waterproof breathable membrane of the present invention may have high moisture permeability in the film thickness direction. Thereby, for example, it becomes possible to discharge | emit the water vapor which stayed inside the housing more quickly to the exterior of the housing by the above-mentioned cause.

The thickness of the waterproof ventilation membrane of the present invention is, for example, 5 to 60 µm, preferably 20 to 40 µm.

The waterproof ventilation membrane of the present invention may be subjected to a coloring treatment. The color of the PTFE porous membrane which has not been subjected to the coloring treatment and the color of the waterproof ventilation membrane provided with the porous membrane is usually white. When such a waterproof ventilation membrane is arrange | positioned so that the opening of a housing may be closed, the said membrane may be outstanding. The prominent membrane stimulates the curiosity of the user, and the function as the waterproof breathable membrane may be impaired by stabbing with a needle or the like. If the waterproof ventilation membrane is subjected to a coloring treatment, for example, the user's attention can be relatively suppressed by setting the membrane to have a color that is the same as or similar to the color of the housing. In addition, a colored waterproof breathable membrane may be required, and such a request can be made by the coloring treatment.

A coloring process can be performed by dyeing a PTFE porous membrane, for example, or including a coloring agent in a PTFE porous membrane. You may perform coloring process so that light contained in the wavelength range of 380 nm or more and 500 nm or less may be absorbed, for example. In this case, the waterproof ventilation membrane can be colored with blue, gray, brown, pink, green, yellow and the like. The waterproof ventilation membrane may be colored in black, gray, brown or pink.

The waterproof ventilation membrane of the present invention may be provided with any member other than the PTFE porous membrane of the present invention. The member is, for example, the breathable support layer 13 shown in FIG. 5. The waterproof breathable membrane 11 shown in FIG. 5 is provided with the PTFE porous membrane 12 of this invention, and the breathable support layer 13 arrange | positioned at one main surface of the porous membrane 12. As shown in FIG. By arrange | positioning the breathable support layer 13, the intensity | strength as the waterproof ventilation film 11 improves, and also handleability improves.

The breathable support layer 13 is preferably a layer having high air permeability and moisture permeability in the thickness direction compared to the PTFE porous membrane 12. As the breathable support layer 13, a woven fabric, a nonwoven fabric, a net, or a mesh can be used. Materials constituting the breathable support layer 13 are, for example, polyester, polyethylene, and aramid resin. The shape of the breathable support layer 13 may be the same as or different from the shape of the PTFE porous membrane 12. For example, it may be a breathable support layer 13 having a shape disposed only at the periphery of the PTFE porous membrane 12 (specifically, in the case where the PTFE porous membrane 12 is circular, a ring-shaped disposed only at the periphery thereof). have. The breathable support layer 13 is disposed by a method such as thermal welding with the PTFE porous membrane 12, adhesion with an adhesive, or the like. The breathable support layer 13 may be disposed on one main surface of the PTFE porous layer 12 or may be disposed on both main surfaces.

The waterproof air permeable membrane of the present invention can exhibit each characteristic exhibited by the above PTFE porous membrane of the present invention.

An example of the waterproof ventilation member of this invention is shown in FIG. The waterproof breathable member 21 shown in FIG. 6 is a waterproof breathable membrane 11 having a circular shape in a direction perpendicular to the main surface of the membrane, and a support 22 which is a ring-shaped sheet bonded to the periphery of the membrane 11. It is provided. By the form in which the support body 22 was bonded to the waterproof ventilation film 11, while the waterproof ventilation film 11 is reinforced, the handling property improves. Moreover, since the support body 22 is provided with the installation allowance to the part in which the waterproof ventilation member 21 is arrange | positioned, such as an opening of a housing, the installation operation of the waterproof ventilation membrane 11 becomes easy.

The shape of the support body 22 is not limited. For example, as shown in FIG. 7, the support body 22 which is a frame-like sheet | seat joined to the periphery of the waterproof air permeable film 11 which is rectangular in shape as seen from the direction perpendicular | vertical to the principal surface of a membrane may be sufficient. As shown in FIG. 6 and FIG. 7, by making the shape of the support 22 into the shape of the periphery of the waterproof breathable membrane 11, the decrease in the air permeability of the waterproof breathable membrane 11 due to the arrangement of the support 22 is reduced. Suppressed. In addition, the sheet-like support 22 is preferable in view of the handleability of the waterproof ventilation member 21 and the disposition in the housing, in particular in the housing. In the example shown in FIGS. 6 and 7, except for the peripheral portion where the support 22 is arranged, the waterproof ventilation membrane 11 is exposed (both surfaces of the waterproof ventilation membrane 11 are exposed).

The material which comprises the support body 22 is resin, a metal, and these composite materials, for example. Resin is polyolefin, such as polyethylene and a polypropylene, for example; Polyesters such as polyethylene terephthalate (PET) and polycarbonate; Polyimide or composites thereof. The metal is a metal excellent in corrosion resistance such as stainless steel or aluminum, for example.

The thickness of the support body 22 is 5-500 micrometers, for example, and 25-200 micrometers is preferable. In addition, focusing on the function as an installation margin, about 0.5-2 mm is suitable for ring width (frame width: the difference of an external shape and an internal diameter). As the support 22, a foam made of the above resin may be used.

The bonding method of the waterproof ventilation membrane 11 and the support body 22 is not specifically limited, For example, methods, such as a heat welding, ultrasonic welding, adhesion | attachment with an adhesive agent, and adhesion | attachment with a double-sided adhesive tape, can be employ | adopted. The support body 22 itself may be a double-sided adhesive tape.

The waterproof ventilation member 21 may be provided with two or more waterproof ventilation membranes 11 and / or two or more support bodies 22.

The waterproof ventilation member of the present invention can be used for the same purposes as the conventional waterproof ventilation member.

The PTFE porous membrane of this invention can be manufactured by the manufacturing method of the PTFE porous membrane shown below, for example. The PTFE porous membrane of the present invention can be a membrane obtained by the method for producing a PTFE porous membrane shown below.

In the method for producing the PTFE porous membrane disclosed herein (the production method of the present disclosure):

Extending | stretching an unbaked PTFE sheet in predetermined direction on the extending | stretching conditions of extending | stretching temperature more than melting | fusing point of PTFE, and extending | stretching linear velocity of 1.0 m / min or less (stretching A);

The sheet stretched by the stretching A is further stretched in a direction different from the predetermined direction (stretching B).

(Extension A)

In the stretching A, the specific method is not particularly limited as long as the unfired PTFE sheet is stretched at a drawing speed of 1.0 m / min or less at a temperature equal to or higher than the melting point (327 ° C.) of PTFE. For example, what is necessary is just to extend | stretch an unbaked PTFE sheet, maintaining the extending | stretching linear velocity of 1.0 m / min or less in the heating furnace maintained at the temperature more than the said melting | fusing point. In the stretching A, after the stretching B, an agglomerated portion of PTFE, which is a precursor of the node, can be formed which can be a long node while having a small area ratio to the area of the film. The aggregated portions may be formed in plural in the PTFE sheet with adjacent aggregated portions close to parallel to each other. The direction in which the said aggregation part extends is a direction substantially perpendicular | vertical in a sheet surface with respect to the extending | stretching direction of extending | stretching A typically. Moreover, in extending | stretching A, the fibrill which can achieve 50 micrometers or more of average fibril length after extending | stretching B can be formed. The direction in which the fibrils extend may be a direction substantially perpendicular in the sheet surface with respect to the direction in which the agglomerated portion extends.

Although the direction (predetermined direction) of extending | stretching A is not specifically limited, For example, when it is MD direction of a PTFE sheet, and the said sheet | seat is a strip | belt-shaped, it may be the long side direction.

The draw ratio of draw A is 8-50 times, for example, Preferably it is 15-35 times.

The temperature (stretching temperature) which performs extending | stretching A should just be more than melting | fusing point of PTFE, for example, 350-420 degreeC, Preferably it is 360-400 degreeC.

The stretching linear velocity of the stretching A is 1.0 m / min or less, preferably 0.5 m / min or less. In addition, the reference length of extending | stretching linear velocity shall be 1.5 m. For example, extending | stretching with a linear linear velocity of 1.0 m / min or less is extending | stretching extending | stretching the said sheet | seat at the speed of 1.0 m / min or less in the direction of the said reference length, when a sheet of reference length 1.5m is assumed. When the sheet is stretched by a pair of rolls having a running speed difference, the traveling distance of the sheet between the pair of rolls (the traveling distance from contacting a subsequent roll after separating the preceding roll) is determined. It can be set as a reference length.

(Stretch B)

In extending | stretching B, as long as the PTFE sheet which passed through extending | stretching A is extended in the direction different from the direction of extending | stretching A, the specific method is not limited.

Although the direction of extending | stretching B is not specifically limited, Typically, it is a direction substantially perpendicular in a sheet surface with respect to the direction of extending | stretching A. FIG. The direction of extending | stretching B is a TD direction of a PTFE sheet, for example, and when the said sheet | seat is a strip | belt-shaped, it may be the width direction.

The draw ratio of draw B is 2-15 times, for example, Preferably it is 4-10 times.

The temperature (stretching temperature) which performs extending | stretching B may be more than melting | fusing point of PTFE, or may be less than melting | fusing point, for example, it is 100-400 degreeC, Preferably it is 120-200 degreeC.

The extending | stretching linear velocity of extending | stretching B is not limited, For example, they are 3 m / min-16 m / min.

In the manufacturing method of this indication, you may perform arbitrary extending | stretching other than extending | stretching A and extending | stretching B as needed. However, it is preferable that extending | stretching performed initially with respect to a PTFE sheet is extending | stretching A. FIG. Moreover, it is preferable that extending | stretching to the said predetermined direction is only extending | stretching A. In the production method of the present disclosure, only the stretching A and the stretching B may be performed as the stretching of the PTFE sheet. The stretching B may be performed continuously after the stretching A.

The method for forming the unbaked PTFE sheet used in the production method of the present disclosure is not particularly limited, and for example, a mixture of PTFE fine powder (fine powder) and a liquid lubricant may be used by at least one method selected from extrusion and rolling. It can be formed by molding into a sheet. It is preferable to remove a liquid lubricant from a PTFE sheet by methods, such as a heating or extraction, before performing the said extending | stretching A.

The kind of PTFE fine powder is not specifically limited, A commercially available product can be used. Commercially available PTFE fine powders include, for example, Polyfron F-104 (made by Daikin Co., Ltd.), Fluon CD-123, Fluon CD-129E (manufactured by Asahi ICI Fluoropolymers), Teflon 6J (Mitsui DuPont Fluorine). Local chemical).

The liquid lubricant can be wetted with the surface of the fine PTFE powder, and is not particularly limited as long as it is a substance that can be removed by means such as evaporation and / or extraction after molding the mixture into a sheet form. Specific examples of the liquid lubricants include hydrocarbon oils such as liquid paraffin, naphtha, white oil, toluene, and xylene, various alcohols, ketones, and esters.

The mixing ratio of the fine PTFE powder and the liquid lubricant can be adjusted depending on the type of the fine PTFE powder and the liquid lubricant, the molding method of the PTFE sheet, and the like, and the liquid lubricant is generally about 5 to 50 parts by weight based on 100 parts by weight of the fine PTFE powder.

The specific method of extrusion and rolling is not specifically limited, For example, after extrusion-molding the said mixture into a rod shape, you may shape | mold the obtained rod-shaped molded object into a sheet form by rolling, and even if this mixture is extrusion-molded into a sheet form, do.

The thickness of an unfired PTFE sheet can be suitably adjusted with the thickness of the PTFE porous membrane to obtain, and is about 0.05-0.5 mm, for example.

In the manufacturing method of this indication, arbitrary processes can be performed after extending | stretching B as needed. The said arbitrary process is a baking process, a liquid repellent treatment, and a sticking process, for example.

In the firing step, the PTFE sheet after the stretching B (PTFE porous membrane formed via the stretching B) is heated to a temperature above the melting point of PTFE and heat treated. The specific method of heat treatment is not limited, For example, what is necessary is just to accommodate the PTFE sheet after extending | stretching in the heating furnace maintained at the temperature more than the said melting | fusing point.

It is preferable to perform heat processing in the state which fixed the dimension of a PTFE sheet. As for the temperature of heat processing, about 350-400 degreeC is preferable. The heat treatment may be performed continuously after the stretching B.

A well-known method can be applied to the liquid repellent treatment.

The sticking treatment is performed by contacting a PTFE sheet after stretching B (PTFE porous membrane formed via stretching B) with a liquid having a low surface tension, thereby forming a blood formed through stretching A in the predetermined direction and stretching B in the different directions. It is a brill and a process which binds several adjacent fibrils. By this treatment, for example, the PTFE porous membrane 1 as shown in FIG. 4 is formed.

The sticking treatment can be performed, for example, by immersing the PTFE sheet after stretching B in a liquid having a low surface tension. The PTFE sheet immersed for a predetermined time may be taken out of the liquid and then dried. You may immerse the PTFE sheet after extending | stretching B which bonded reinforcement layers, such as a nonwoven fabric, in liquid. Thereby, the sticking process can be performed more stably and reliably.

The low surface tension liquid may be a liquid having a low surface tension that can penetrate between the fine fibrils of the PTFE sheet (PTFE porous membrane) after stretching B. Specifically, the surface tension of the liquid is 30 mN / m or less, preferably 25 mN / m or less. The said liquid is alcohol, such as methanol and ethanol, ether, for example. Commercially available liquids such as 3M, hydrofluoroether Novec (registered trademark) may also be used as the liquid.

When performing a baking process and a liquid repelling process and / or sticking process, it is preferable to perform a liquid repelling process and a sticking process later than a baking process.

By the manufacturing method of this indication, PTFE porous membrane A can be manufactured, for example.

As long as the effects of the present invention are obtained, the production method of the present disclosure may include any steps other than those described above.

EXAMPLE

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to the following examples.

First, the evaluation method of the PTFE porous membrane produced in the present Example is shown.

[Average Fibrillation Length, Average Node Length, Average Node Area Ratio]

The average fibril length, average node length, and average node area ratio of the PTFE porous membrane were obtained by SEM (JSM-6510LV, manufactured by JEOL) and obtained an enlarged image of the main surface of the PTFE porous membrane to be evaluated.

[Average curve rate]

The average curvature rate in the film thickness direction of a PTFE porous membrane was calculated | required by the method mentioned above.

[Waterproof]

The water resistance of the PTFE porous membrane was evaluated by the water resistance measured in accordance with the provisions of the water resistance test B method (high water pressure method) of JIS L1092: 2009. However, the water pressure resistance was evaluated based on the water pressure when water came out from one place of the membrane surface of the PTFE porous membrane.

[Porosity rate]

The porosity of the PTFE porous membrane was determined by the method described above.

[Moisture permeability]

Evaluation method 1: The water vapor transmission rate of the PTFE porous membrane was evaluated based on the specification (water vapor transmission test, the cup method) of JISZ0208: 1976. However, at the time of evaluation of moisture permeability, the atmosphere on one main surface side of a PTFE porous membrane was made into temperature 40 degreeC, and humidity 100% RH, and the atmosphere of the other main surface side was made into temperature 40 degreeC and humidity 50% RH.

Evaluation method 2: The water vapor transmission rate of the PTFE porous membrane was evaluated based on the specification of JIS L1099: 2012 (B-1 method; potassium acetate method). In addition, the water vapor transmission rate of the predetermined | prescribed moisture permeability measurement film used in this prescription exists in the range of 75000-85000g / (m <2> * day) by this JIS measurement. The water vapor transmission rate of an auxiliary film can be measured by using two auxiliary films, making one the auxiliary film and the other the film of a measurement object.

(Example 1)

PTFE paste was formed by uniformly mixing 100 parts by weight of PTFE fine powder (manufactured by Asahi ICI fluoropolymer, Fluon CD-129E) and 19.7 parts by weight of aliphatic hydrocarbon as a liquid lubricant. Subsequently, the formed PTFE paste was extruded into a sheet shape at a pressure of 2.5 MPa (25 kg / cm 2) using an FT die, and further rolled with a pair of metal rolls to form a strip-shaped PTFE sheet. (Thickness 0.2 mm) was obtained. Subsequently, the obtained PTFE sheet was heated and dried to remove the liquid lubricant.

Subsequently, it uniaxially stretched in the longitudinal direction at the extending linear velocity of 0.4 m / min in the heating furnace hold | maintained at 360 degreeC, supplying the strip | belt-shaped PTFE sheet after drying continuously (stretching A). The draw ratio at this time was 20 times.

Next, the PTFE sheet after extending | stretching A was uniaxially stretched in the width direction at the extending | stretching linear velocity of 12 m / min in the heating furnace hold | maintained at 130 degreeC (stretching B). The draw ratio at this time was 5 times. In this way, the PTFE stretched porous membrane of Example 1 was obtained. The SEM observation image of the PTFE porous membrane of Example 1 is shown in FIG.

(Example 2)

The porous porous membrane produced in Example 1 was impregnated with 3M product, hydrofluoroether Novec7300, and the sticking process was performed to the porous membrane. The PTFE porous membrane after the impregnation was dried to obtain a PTFE porous membrane of Example 2. The SEM observation image of the PTFE porous membrane of Example 2 is shown in FIG.

(Example 3)

The PTFE porous membrane of Example 3 was obtained in the same manner as in Example 1 except that the stretching linear velocity of the stretching A was 0.8 m / min.

(Example 4)

The PTFE porous membrane produced in Example 3 was subjected to sticking in the same manner as in Example 2 to obtain a PTFE porous membrane of Example 4.

(Comparative Example 1)

PTFE paste was formed by uniformly mixing 100 parts by weight of PTFE fine powder (manufactured by Asahi ICI fluoropolymer, Fluon CD-129E) and 19.7 parts by weight of aliphatic hydrocarbon as a liquid lubricant. Subsequently, the formed PTFE paste was extruded into a sheet shape at a pressure of 2.5 MPa (25 kg / cm 2) using an FT die, and further rolled with a pair of metal rolls to form a strip-shaped PTFE sheet. (Thickness 0.5mm) was obtained. Subsequently, the obtained PTFE sheet was heated and dried to remove the liquid lubricant.

Subsequently, it uniaxially stretched in the longitudinal direction at the extending linear velocity of 12 m / min using the heating roll maintained at 100 degreeC, supplying the strip | belt-shaped PTFE sheet after drying continuously. The draw ratio at this time was 4 times.

Next, the PTFE sheet after the stretching was further uniaxially stretched in the longitudinal direction at a stretching linear velocity of 1.5 m / min in a heating furnace maintained at 380 ° C. The draw ratio at this time was 8 times.

Next, the PTFE sheet after the stretching was uniaxially stretched in the width direction at a stretching linear velocity of 12 m / min in a heating furnace maintained at 130 ° C. The draw ratio at this time was 5 times. The SEM observation image of the PTFE porous membrane of Comparative Example 1 thus obtained is shown in FIG. 10.

(Comparative Example 2)

PTFE paste was formed by uniformly mixing 100 parts by weight of PTFE fine powder (manufactured by Asahi ICI fluoropolymer, Fluon CD-129E) and 19.7 parts by weight of aliphatic hydrocarbon as a liquid lubricant. Subsequently, the formed PTFE paste was extruded into a sheet shape at a pressure of 2.5 MPa (25 kg / cm 2) using an FT die, and further rolled with a pair of metal rolls to form a strip-shaped PTFE sheet. (Thickness 0.5mm) was obtained. Subsequently, the obtained PTFE sheet was heated and dried to remove the liquid lubricant.

Subsequently, it uniaxially stretched in the longitudinal direction at the extending linear velocity of 6 m / min using the heating roll maintained at 150 degreeC, supplying the strip | belt-shaped PTFE sheet after drying continuously. The draw ratio at this time was 4 times.

Next, the PTFE sheet after the stretching was further uniaxially stretched in the longitudinal direction at a stretching linear velocity of 1.5 m / min in a heating furnace maintained at 380 ° C. The draw ratio at this time was 8 times.

Next, the PTFE sheet after the stretching was uniaxially stretched in the width direction at a stretching linear velocity of 12 m / min in a heating furnace maintained at 130 ° C. The draw ratio at this time was 5 times. Thus, the PTFE stretched porous membrane of the comparative example 2 was obtained. The SEM observation image of the PTFE porous membrane of the comparative example 2 is shown in FIG.

(Comparative Example 3)

The PTFE porous membrane produced in Comparative Example 2 was subjected to sticking treatment in the same manner as in Example 2 to obtain a PTFE porous membrane of Comparative Example 3.

The evaluation result of the PTFE porous membrane produced in each Example and the comparative example is shown in the following Table 1.

As shown in Table 1, the PTFE porous membrane of the Example showed high moisture permeability in the film thickness direction compared with the PTFE porous membrane of the comparative example. In addition, the PTFE porous membranes of Examples 1 and 3 reduced the average curvature ratio by the sticking treatment and improved the moisture permeability in the film thickness direction. However, the PTFE porous membrane of Comparative Example 2 also had the average curvature ratio and the sticking treatment. The moisture permeability of the film thickness direction did not change.

The present invention can be applied to other embodiments without departing from the intention and essential features thereof. Embodiment disclosed in this specification is explanatory at all points, and is not limited to this. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are embraced therein.

The PTFE porous membrane of the present invention can be used, for example, as a waterproof ventilation membrane.

Claims (8)

A polytetrafluoroethylene porous membrane having an average fibril length of 50 µm or more, an average node length of 5 times or more of an average fibril length, and an average node area ratio of 5% or less. The polytetrafluoroethylene porous membrane of Claim 1 whose said average node area ratio is 3% or less. The polytetrafluoroethylene porous membrane of Claim 1 or 2 whose average curvature ratio in a film thickness direction is 1.5 or less. The polytetrafluoroethylene porous membrane according to any one of claims 1 to 3, wherein the water pressure measured in accordance with the provisions of the water resistance test B method (high water pressure method) of JIS L1092 is 10 kPa or more. The polytetrafluoroethylene porous membrane as described in any one of Claims 1-4 whose porosity is 90% or more. The polytetrafluoroethylene porous according to any one of claims 1 to 5, wherein the water vapor transmission rate in the film thickness direction measured in accordance with the provisions of JIS L1099 (B-1 method) is 150000 g / (m 2 · day) or more. membrane. The waterproof breathable membrane provided with the polytetrafluoroethylene porous membrane in any one of Claims 1-6. The waterproof breathable member provided with the waterproof breathable membrane of Claim 7, and the support body joined to the waterproof breathable membrane.

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